The invention relates to pressure relief valves which are known as safety valves and are generally used with pressurized vapor containments, and more particularly to an improvement in drip pans associated with such valves.
Pressurized vessels and conduits associated with vapor generators are equipped with safety valves which provide the means for relieving excessive vapor pressure buildup thereby precluding damage to the pressure parts. Generally, the safety valve forms part of a series of components which disposes of the released vapor either to atmosphere or to an auxiliary vessel, and includes a vent, an exhaust pipe, a hood, and a drip pan with the latter surrounding the outlet end of the vent pipe to collect condensate drippings from the released vapor. The drip pan, the hood and the exhaust pipe are normally secured to a fixed framework whereas the vent pipe is fastened to the safety valve and the latter is secured to the vessel or conduit associated therewith. It should be recognized that whenever a vapor generator is placed into or taken out of service, it and its associated vessels and conduits will undergo thermal expansion or contraction thereby causing the safety valve and vent pipe to shift relative to the drip pan and exhaust pipe, the latter two being secured to the fixed framework. It is general practice in the prior art to furnish a drip pan having an opening of considerably greater cross-sectional area than that of the vent pipe extending therethrough so as to provide the clearance necessary to accommodate horizontal movement of the vent pipe occasioned by expansion or contraction of the vapor generator, the vessels and the conduits associated therewith.
The drip pan must be dimensioned to house an annular plate which is slidably fitted to the vent pipe and is sized to maintain a closure over the drip pan opening, throughout the range of movement of the vent pipe. This prior art construction has the disadvantage of requiring a relatively large drip pan which is unsuitable for the narrow confines and limited spacing generally alloted to safety valves associated with vapor generators.